The invention relates to a modular steering column mounted switch system for a motor vehicle.
Modular steering column mounted switches are disclosed in DE 2,810,790 and WO 95/13936. These steering column mounted switches have a modular construction which is defined by the technical requirements of assembly or of installation in a vehicle or which has a modularity determined by the external functions to be executed by the switch, such as operation of the light systems or of the window washing systems. The modularity does not reflect a division dictated by the different internal functions of the switch, such as the reception of external mechanical signals, the processing of internal mechanical signals, the mechanical switching of electrical switches, and/or the electrical switching and control of load current and of control current. These various internal functions of the switch assemblies are all integrated in a single module. Requisite electrical subassemblies for the switching and control of load and control currents, the switches and mechanical components for external operation of the switch functions as well as the current terminal connections to the external assemblies which are to be controlled (lights, blinkers, signal horn etc.) are combined, to the greatest possible extent, into one single module. In these conventional steering column mounted switches, failure of one internal function disadvantageously causes the overall module to be defective and to require replacement. In addition, a specific modification of the switch system to the functional needs and design requirements of certain motor vehicles cannot be realized by only changing the components and assemblies that are affected, rather the entire module must be reconfigured.
In view of these deficiencies in prior art, it is the purpose of the present invention to introduce a steering column mounted switch which is more economical to produce and to repair.
This purpose is achieved in accordance with the present invention with a steering column mounted switch having modules which are configured and assembled in accordance with functional and design requirements and which may be individually replaced in case of defect.
The modular construction of the switch in accordance with the invention is therefore defined by its internal functions. These internal functions of the switch include the accommodation of functional subassemblies and their mounting to the steering column, the receiving and processing of external mechanical signals as well as the switching and control of internal electrical signals. The inventive structure facilitates flexibility in functional group combinations as required by the application. The subdivision of the inventive switch into modules according to function makes repair and maintenance considerably more economical since only defective parts must be replaced. In addition, manufacture is considerably more economical since higher piece counts can be produced.
In accordance with the invention, the different functions required of a steering column mounted switch are consistently assigned to separate individual modules which are detachable from each other and which, when assembled, form the entire switch. For example, one or more modules may be provided which have mechanical functions only to convert the manual operation of the driver (e.g. twisting or turning with respect to the steering column) into a corresponding mechanical movement of a switch member. The at least one mechanical module cooperates with at least one additional module which substantially performs electrical functions only such as electrical connections and optionally electrical amplification and filtering. There is therefore a clearly separated boundary between mechanical and electrical operations. These functions are then combined via interfaces between the corresponding modules. A module may also be provided which exclusively serves to anchor the other modules to the steering column in a simple way. Such a module therefore serves to receive functional subassemblies and to mount them to the steering column. Another module may also be provided which performs a measuring function, e.g. measuring the turning angle of the steering wheel and, consequently, of the steering column relative to the retaining case of the steering column, wherein the steering column mounted switch is mounted to that retaining case.
When a desired change is performed on a switch, this is usually directed to a certain function. For example, it is possible that only the external design of a switch lever module is to be changed or adapted to the spatial conditions of a new type of motor vehicle. In this event, only the associated module or modules must be modified and the construction of the module having the electrical circuit connections need not be changed. In addition, a module which carries electrical circuits may be furnished having built-in auxiliary features to enable new switching functions in conjunction with the insertion of a corresponding mechanical module to e.g. convert switching movements made by the driver into corresponding contact changes on the electrical module (electric board).
Conversely, certain mechanical movements of a shift lever may be assigned new electrical functions. In this case, only an electrical module must be replaced while the mechanical module(s) may remain unchanged. By changing the mounting module used to mount all of the other modules to the steering column housing, a switch can be adapted to different housings and, consequently, to different types of motor vehicles with the remainder of the switch advantageously remaining unchanged. The invention is therefore particularly well suited for adapting a switch to new electrical or mechanical requirements, since only one of the corresponding modules must be replaced. This is also the case in the event that new technical developments are to be incorporated.
In a preferred embodiment in accordance with the invention, the steering column module has a signal transmission case for transmitting information and/or electric currents between the steering wheel and the motor vehicle, with a steering angle sensor comprising a first evaluation electronics, at least one steering column switch and at least one second evaluation electronics for the signal transmission case and/or the steering column switch(es), wherein the first evaluation electronics and the second evaluation electronics are disposed close to one another.
This preferred embodiment reduces the space requirements for the steering column module. This is of great importance for future automotive development since the specifications of automobile manufactures have become more and more restrictive with respect to available space. A further advantage of this embodiment is that the plug paths required for contacting the different units of the steering column module are reduced, thereby facilitating assembly and reducing the likeliness of assembly errors. This produces improved operational safety of the steering column module and improved reliability of the electronics. Moreover, the complete steering column module can be assembled and its function tested outside of the vehicle.
A first variation of this embodiment of the invention provides that the first evaluation electronics and the second evaluation electronics are disposed between the signal transmission case and the steering column switch to save space substantially in the region of the steering column module facing away from the steering wheel of the vehicle.
An alternative to this variation provides that the first evaluation electronics and the second evaluation electronics are integrated in the steering angle sensor. This saves additional space and reduces the number of units.
Another variation of this preferred embodiment provides that the first evaluation electronics and the second evaluation electronics are disposed on a common printed circuit board. This facilitates production of the first and second evaluation electronics and its assembly in the steering column module and also further improves the reliability of the electronics.
In a further alternative, an electric plug connection is provided between the signal transmission case and the second evaluation electronics, wherein their assembly also establishes the electric contacts.
According to an advantageous variation of the preferred embodiment of the invention, one electric plug connection is provided between each steering column switch and the second evaluation electronics, wherein assembly also establishes electric contact among these units.
In a further alternative, the steering angle sensor is disposed between the signal transmission case and steering column switch, wherein the plug paths are particularly short.
In accordance with a further variation, the signal transmission case comprises a part which can be rotated with the steering wheel of the automotive vehicle, wherein the steering angle sensor comprises a code disc which is rotatably disposed in the steering angle sensor, and the code disc is connected for secure rotation with the rotary part of the signal transmission case. Displacement of the code disc from the signal transmission case to the steering angle sensor leavesxe2x80x94with identical outer dimensionsxe2x80x94more space for one or two broad-band cables to transfer the signals and electric currents from the steering wheel to the vehicle and vice versa. This is important, in particular for modern vehicles since more and more functions are performed from the steering wheel.
In another alternative, the first steering column switch operates the blinker and includes a blinker return position, wherein the blinker return position can be controlled by the steering angle sensor. In this manner, the steering column module can function prior to installation in the vehicle and that function can be checked before assembly.
Further advantages and advantageous embodiments of the invention can be extracted from the following description, the drawing, and the claims. Embodiments of the subject matter of the invention are represented in the drawing and explained in more detail below.